A fuel cell system is a power generation system that receives hydrogen as a fuel and oxygen in the air and generates electrical energy by an electrochemical reaction between hydrogen and oxygen in a fuel cell.
For example, a fuel cell system is applied to a fuel cell vehicle and operates the vehicle by powering an electric motor by electrical energy produced by a fuel cell.
In general, such fuel cell system includes a fuel cell stack which is an assembly of fuel cells each including of an cathode and a anode, an air supplier for supplying air to the cathode, and a hydrogen supplier for supplying hydrogen to the anode.
When the fuel cell system generates power, the cathode produce water and a portion of the water is moved to the anodes through an electrolyte layer of the stack due to concentration differences.
Accordingly, gases including unreacted hydrogen and water coming from the cathodes are discharged from the anodes of the fuel cells. The gases and the water are re-supplied to the fuel cell stack through a hydrogen recirculation device, and condensed water is discharged from the anodes after being temporarily stored in a water trap, and is later discharged to the outside of the fuel cell stack.
The gases including unreacted hydrogen are generally purged when recirculating the gases to remove impurities besides hydrogen discharged from the anodes of the fuel cell stack. As a result, this purging increases the concentration of hydrogen supplied to the anodes and activates electrochemical reactions in the stack.
If the condensed water in the anodes is not properly discharged to the outside, the stack may be filled with condensed water and hydrogen may not move to the cathodes through the electrolyte layer. This may cause reduced output and serious problems in driving the vehicle. As such, the discharge of condensed water as well as the purging of hydrogen-containing gases may be critical for operating the fuel cell system.
Typically, each of a purge valve and a drain valve is applied to a water trap that connects a gas and water discharge line which is from the anodes of a fuel cell stack and a hydrogen recirculation line or to the front and back end of the water trap. These valves may perform gas purging and discharging condensed water independently. In other words, the purge line and the drain line are separated from each other.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.